Illumination sources, also referred to as illuminates or illuminants herein, may not be pure white, but instead have a bias towards a particular color. The color bias is usually measured in terms of a color temperature. Human eyes can compensate for illumination that is not pure white, so colors appear relatively consistent over a wide range of lighting conditions. In other words, human eyes can adjust to different lighting conditions so that gray objects appear gray (grey and gray may be used interchangeably herein).
Electronic sensors, however, may perceive the same scene differently when the illuminant changes. Electronic sensors capture images but may be unable to compensate for different lighting conditions having different color temperatures. A typical sensor used in an electronic image capture device, such as a digital camera or video recorder, may capture an image that exhibits a color shift attributable to illumination from a non-pure white source. The color shift exhibited in the captured image may appear unnatural to the human eye and create a perception that the sensor or capture device is of low quality, i.e., unable to accurately capture real world images.
A captured image may be processed to compensate for lighting conditions and color temperature of the illuminant. White balance compensation depends on the color temperature of the illuminant. White balance compensation configured for an illuminant at a first color temperature may not correct for color temperature of a second illuminant, and may further degrade image quality by introducing additional color shift into the image. When color tone in a digital image is off, i.e., no white balancing or incorrect white balancing, human perception of the image may be objectionable.